The present invention concerns devices and methods for ensuring a desired central and rotational alignment of structural parts of a wind turbine during their assembly and connection. The structural parts are traditionally connected in a flange-to-flange connection by a number of bolts. For a proper connection, the flanges need to be centrally aligned so that the flanges are positioned face-to-face and further rotationally aligned so that the boreholes of the flanges match. The structural parts of a wind turbine such as a tower section, a foundation section, a blade, a yaw bearing or the like, are big and heavy components and their connection involve large cranes or other types of hoisting equipment and need to be performed on site often under non-ideal conditions such as at sea, in non-even terrain etc.
Traditionally the central and rotational alignment of structural parts, such as two wind turbine tower sections, or a tower section onto a foundation section, is performed by the matching of outside visual markers on both structural parts which however can only be performed with some uncertainty. The final adjustment is then obtained by man power by simply rocking the flanges into position by the use of a mandrel through a borehole.
To increase personnel safety the assembly of such structural parts should ideally be carried out without any personnel remaining inside the hollow tower or foundation section anywhere near where the structural parts are to be connected. Furthermore, in addition to being centrally and rotationally aligned to make the boreholes in the flanges match, the structural parts also need to be rotationally aligned in a specific way to make other components fit and connect such as ladders, wiring, cable trays, elevators etc. These may for the most part be positioned inside the structural parts and thereby at least partly invisible and not usable for guidance during the assembly of the structural parts.